is it possible to cycle only some keyframes in the graph editor?
No, not in the graph editor, you should use NLA editor for this.

in the graph editor you can setup repeating all bunch of keyframes, not part of it.

First, set up cycles in action editor, each cycle in different action:



Then use Push Down in action editor or Shift+A in NLA Editor to add actions in NLA:



Then in NLA editor's N-panel (properties panel) you can set up any count of cycles using repeat property: